Fuji Portaflow-C FSC-4 Replacement Battery 7.4V 2600mAh

Fuji Portaflow-C FSC-4 Series — 7.4V Li-ion Replacement Battery (FSC)

This 7.4V 2600mAh Li-ion battery fits the Fuji Portaflow-C FSC-4 ultrasonic flow meter and compatible FSC, FSC3, and FSC4 variants. It replaces the original OEM pack using the same connector pinout and BMS communication protocol. Capacity is 2600mAh (19.24Wh), matching the original specification.

• FSC series compatibility: The FSC, FSC3, and FSC4 share the same 7.4V battery bay, connector orientation, and BMS handshake requirements. Swapping between these models does not require firmware changes or hardware modifications.
• Bench tested on actual hardware: We cycled this pack through the FSC-4's probe initialisation sequence, which draws a brief current spike as the transducers power up. The BMS held without triggering an overcurrent cutoff across repeated cold-start cycles.
• Pre-deployment calibration cycle: After fitting this battery, run a full calibration cycle through the instrument menu before heading into the field. The FSC-4 maps battery state during calibration — skipping it causes the low-battery indicator to fire prematurely on the first measurement session.

BMS lockout after the FSC-4 sat unused in a carry case for months

Li-ion cells self-discharge over time. If the FSC-4 sits unused long enough, the pack drops below the BMS recovery threshold — typically around 2.5V per cell — and the protection circuit locks out to prevent damage. At this point the instrument shows no sign of life and a standard charger may not initiate a charge cycle. The fix is to apply a trickle charge using a bench supply set to 7.4V at 100–200mA for 15–20 minutes to nudge the cell voltage above the recovery floor, then switch to the standard charger.

Flow readings resetting or drifting partway through a logging session

This is not a sensor fault — it is a voltage dropout under sustained load. The FSC-4 draws consistent current across the transducer pair during active logging, and a degraded or partially discharged cell cannot hold voltage steady under that load. The micro drops just enough to trigger a soft reset of the logging module, which clears the active session. Check cell voltage under load with a multimeter; if it sags below 6.8V during active measurement, the pack needs replacing rather than recharging.